This invention relates to a generator cooling apparatus having a plurality of selectively energized motor driven fans.
In general, the fan function of the rotor of a generator may be used to self-cool the generator. However, since the cooling ability of such a system is not sufficient to cool a large capacity generator, a separate cooling system is employed including a plurality of motor driven fans disposed around the circumference of the generator.
FIG. 1 shows a large capacity flywheel type generator cooled by a conventional separate cooling system. A flywheel generator utilizes a flywheel for storing electrical energy by converting it to rotary inertial energy, and then releases the rotary inertial energy to reconvert it to electrical energy when required.
In FIG. 1 an upper circular generator pit 2 and a lower circular flywheel pit 3 are formed within a concrete foundation 1. A plurality of ventilating passages 4 are provided within the concrete foundation 1 to connect the generator pit to the flywheel pit. The rotor 5 of the generator is disposed in the generator pit. A flywheel 7 is coupled to the lower end of the rotor shaft 6. A thrust collar 8 is attached to the underside of the flywheel, and is rotatably supported by a thrust bearing 9. A motor 10 is connected to the upper end of the rotor shaft 6. A generator stator 11 is disposed around the rotor 5. A plurality of motor driven fans 12, 13, 14, and 15 are disposed at certain positions within the generator pit 2 to provide cooling air to the rotor 5 and stator 11, as indicated by the arrows.
Each of the conventional motor driven fans 12, 13, 14, and 15 is constructed as shown in FIGS. 2 and 3, wherein a motor 17 is mounted within a circular frame or cowling 16 by support members 18 and drives a fan 19.
The time sequence of various functions of the flywheel generator is shown by line a in FIG. 4. The rotor 5 is initially spun up by the motor 10 until its rotation speed reaches n.sub.1 rpm, whereafter the acceleration ceases and concurrently the generation of electric power is started. Rotary inertial energy stored by the flywheel is converted into electrical energy, which is extracted from the stator 11 of the generator. The rotor speed decreases during generation, and no electric power is extracted after the rotational speed drops to n.sub.2 rpm. The rotor remains at the n.sub.2 speed solely by inertial flywheel energy, and after a certain stand-by period it is again accelerated by the motor 10 up to the n.sub.1 speed.
In such a way the flywheel generator supplies a large amount of electric power according to the load demand. On the other hand, as shown by line b in FIG. 4, the cooling fans 12, 13, 14, and 15 are operated continuously, during both the loaded and unloaded periods of the generator.
Although the flywheel generator supplies electric power according to the demand of various loads, in the case of experimental nuclear fusion devices or the like, the periods of maximum rated output are considerably smaller or less than the periods of low or no output. The ventilation capacity of the fans is necessarily designed for sufficient cooling at the maximum rated output, however, and their continous operation wastefully consumes from 200 kw to 300 kw of electrical power.